The present invention relates to a feeding device and feed storage hopper for laboratory rats which device is used for experimental purposes, and more particularly to such device which restricts bodily entry of the rats into the feeder device.
Experimental rats are used in various studies of diseases, and effects of experimental diets, drugs and other treatments designed to acquire statistical knowledge for the benefit of mankind. It is highly desirable in evaluating the effects of drugs, diet and the like, to eliminate the possibility of errors, and thus misleading results, caused by the excretion of bodily wastes, such as urine and feces, into the food contained in the rat feeder device.
Moreover, current trends in toxicology and safety evaluation concerning modern drugs and medical preparations have necessitated an increase in long-term feeding studies of laboratory animals undergoing tests and observations. In order to provide valid and reliable results relating to food consumption, it has been found that long-term feeding experiments must be conducted under extremely careful feeding conditions.
It is, therefore, extremely important to avoid or prevent food contamination that will occur if the animal is permitted bodily access to food which may then be exposed to animal excretory wastes. In many instances, an animal, such as a rat, may obtain an overdose of drug fed to it by eating food contaminated by fecal matter or urine carrying some percentage of the original drug dosage, thereby inducing false test results and inaccurate observations and calculations. Furthermore, in longterm feeding studies, it is essential to determine exact food and thus drug consumption without losses due to food spillage, while maintaining conditions of utmost cleanliness.
Rat feeding studies in nutritional and toxicological research often require that the test agent be administered in the feed and that the feed and test agent consumption be quantitated. Meal rat feed is the logical choice in many studies of this type.
Feeder systems for computing feed consumption have been developed for use with laboratory mice; Hunziker, J.: A new feeder system for quantitating actual toxicant consumption by feed during feeding studies, Lab. Animal Science, Vol. 25, pp. 85-87, 1975. For example, U.S. Pat. Nos. 3,902,459 and 3,965,868 to Hunziker each show laboratory mouse feeder assemblies including a screen-covered feed container. In Hunziker U.S. Pat. No. 3,965,868 the feed hopper can be hung above the floor inside the animal cage. The laboratory mice are able to insert their needle-like tongues through the screen openings for reaching the feed. However, partition shielding plates subdividing the screen structure prevent the mice from gaining bodily access to the food source and possibly contaminating same by depositing therein bodily excretory wastes. A patent to Mancini U.S. Pat. No. 3,505,977 discloses a rodent feeder assembly for laboratory animals, wherein a trough is provided with a lid having selected opening sizes to provided limited access by the animal to the trough contents for feeding purposes while restricting bodily access thereto thus avoiding food contamination with urine or feces. A published Abstract to Law et al. U.S. application Ser. No. 182,084 shows a laboratory mouse feeder comprising a hopper cover provided with slots to permit the caged rodents to consume the food while preventing bodily entrance of the animal into the hopper thus avoiding possible contamination of the food with animal excretory wastes.
The above prior art laboratory feed devices, particularly those shown by Hunziker, although suitable for smaller size rodents, such as mice, are not fully satisfactory for larger size animals, such as rats. In many cases adult rats were unable to efficaciously reach the feed because either the openings in the screen blocking structures were too small, or in cases where such openings were sufficiently large, the completely attached screened structures prevented the laboratory animals from adequate contact with the food, which was not being continuously fed from the food source, thus leading to distorted research results or discarding of expensively dosed food. The Hoeltge Patent, U.S. Pat. No. 3,114,350 shows a laboratory rat feeder which was not satisfactory for the purposes discussed above because young rats of smaller size were able to gain bodily access to the feed thus contaminating same with bodily excrement. Moreover, the rats were difficult to remove from the feed for weighing purposes. Furthermore, larger rats had difficulties reaching the last portion of food causing either reduced eating, and distored test results, or as mentioned above, uneconomical discarding of the dosed feed.
It has been found that most commercially available rat feeders do not have the capacity to hold 600-700 grams of feed required to maintain three rats for a week. See Nolen, G. A., Alexander, J. C.: Comparison of growth and fat utilization of caesarian derived and conventional albino rats. Laboratory Animal Care, Vol. 15, pp. 295-303, 1965 and Mohn, H. E. and Hopkins, L. L., Jr., An all plastic system for housing small animals in trace element studies, Laboratory Animal Science, Vol. 22, pp. 96-98, 1972. Some feeders, as mentioned above, allow rats to climb inside the feeding area and contaminate the feed as well as block other rats from access to feed. Spillage of feed is often significant through the feed retainer or from rats digging in the food container, which results in erroneous food consumption data. The height and holding brackets of most commercially available feeders do not fit conventional plastic laboratory rat cages causing improper lid closure. Finally, the design of some of the commercial feeders is such that feed which may contain hazardous substances is not readily removed by automatic washing procedures.
On the other hand, the present improved Laboratory Rat Feeder Assembly, as will be more specifically disclosed below, will advantageously overcome these problems of the prior art commercial structures and will more safely and accurately accomplish the medical research purposes discussed above.